Pathways/Tracts

ascending tracts:

dorsal column medial lemniscus

spinothalamic

spinoreticular

DCML function

caries light tough, proprioception, vibration, two-point discrimination

DCML lesion below the medulla:

ipsilateral (SAME SIDE) loss of sensation (light tough, proprioception, vibration, two-point discrimination)

DCML lesion above the medulla:

contralateral (OPPOSITE SIDE) loss of sensation (light tough, proprioception, vibration, two-point discrimination)

DCLM decussion

lower medulla

DCLM entrance

dorsal root ganglia into dorsal horn of spinal cord

spinothalamic tract enterance

dorsal root ganglion in dorsal horn of spinal cord

spinothalamic tract function

conveys pain (nociception), temperature, crude touch, and pressure sensations

spinothalamic tract crosses over at

anterior commissure of the spinal cord 2-3 levels above entry

spinothalamic tract lesion below (hasn't crossed over) level of anterior commissure (lateral)

ipsilateral sensory loss (pain, temperature) at the level of lesion

spinothalamic tract lesion above (crossed over) the level of anterior commissure (anterior)

contralateral sensory loss (crude touch, pressure) 2-3 segments below lesion

anterior portion of the spinothalamic tract

crude touch, pressure

lateral portion of spinothalamic tract

pain, temperature

spinoreticular tract enterance

dorsal root ganglion in dorsal horn of spinal cord

spinoreticular tract function

conveys dull/aching pain, regulates consciousness, attention, arousal, mood, autonomic responses

where does the spinoreticular tract decussate

anterior commissure of spinal cord

once the spinoreticular tract enters the thalamus it:

has diffuse projections

lesion of the spinoreticular tract

reduced arousal/alertness, changes in pain perception, mood/sleep/autonomic disturbances

descending tracts:

corticospinal

rubrospinal

reticulospinal

vestibulospinal

tectospinal

corticospinal tract origin

primary motor cortex and premotor frontal areas

corticospinal tract function

voluntary control of body muscles

distal (lateral tract)

proximal (medial tract)

lateral corticospinal tract crosses over at

pyramidal decussation (medulla)

(90%) -contralateral

medial corticospinal tract crosses over at

they remain uncrossed (10%) ipsilateral

lateral corticospinal tract controls

distal limbs/digits fine skilled movements

medial corticospinal tract controls

proximal limbs/trunk posture and gross movement

corticospinal tract lesion above decussation (crosses over-lateral)

contralateral UMN signs: weakness, spasticity, hyperflexia, Babinski sign

corticospinal tract lesion below decussation (doesn't cross over-medial)

ipsilateral UMN signs below lesion: weakness, spasticity, hyperflexia, Babinski sign

rubrospinal tract function

facilitates flexor tone (wants to stay flexed, fetal position), inhibits extensor tone, fine motor control in contralateral upper limb

rubrospinal tract origin

midbrain, red nucleus

rubrospinal tract decussates at

ventral tegmental decussation in midbrain

immediate crossing

rubrospinal tract lesion

weakness/loss of contralateral upper limb flexion; increased extensor tone; impaired fine movement

vestibulospinal tract origin

vestibular nucleii in pons and medulla

vestibulospinal tract function

maintains posture, balance, head/neck righting reflexes, excites extensors, inhibits flexors

vestibulospinal tract decussates at

lateral: doesn't cross

medial: paritally crosses at brainstem

vestibulospinal tract recieves input from

CN V111

lateral division of the vestibulospinal tract

descends ipsilaterally the entire way

lateral division of the vestibulospinal tract function

excites extensors, inhibits ipsilateral flexors

medial division of the vestibulospinal tract

descends bilaterally to cervical/upper thoracic cord

medial division of the vestibulospinal tract function

head/neck motor control (righting reflexes)

vestibulospinal tract lesion

impaired balance, increased fall risk, poor postural/head control, loss of antigravity muscles tone (poor trunk control)

reticulospinal tract origin

pons (medial)

medulla (lateral)

reticulospinal tract function

regulates posture, balance, muscle tone, reflexes, automatic movements

reticulospinal tract medial (pontine)

descends ipsilateral (doesn't cross over) stimulates extensors, inhibits flexors

reticulospinal tract lateral (medullary)

descends bilaterally (some fibers cross midline) stimulates flexors, inhibits extensors

reticulospinal tract lesion

loss of postural control, abnormal tone, gait disturbance, impaired reflexes

reticulospinal tract terminates at

lower motor neurons in the anterior horn of all spinal levels

tectospinal tract function

reflex postural head/neck movement to visual (some auditory) stimuli, coordinates gaze and orientation

tectospinal tract originates at

midbrain (tectum and superior colliculus)

tectospinal tract decussates at

dorsal tegmental decussation, midbrain

immediate crossing

tectospinal tract lesion

impaired reflexative head/neck turning, difficulty orienting to stimuli, reduced gaze shifting

tectospinal tract terminates at

anterior horn of the cervical spinal or (neck/upper thoracic muscles)

anterior spinocerebellar function

unconscious proprioception from lower limbs, coordination of gait

anterior spinocerebellar decussates

spinal cord (recrosses in cerebellum)

anterior spinocerebellar lesion

ipsilateral ataxia (lower limbs)

posterior spinocerebellar function

fine unconscious proprioception, posture/balance,

posterior spinocerebellar lesion

ipsilateral ataxia

posterior spinocerebellar decussates at

none

cuneocerebellar tract function

unconscious proprioception from upper limbs, coordination

cuneocerebellar tract lesion

ipsilateral ataxia (upper limbs)

cuneocerebellar tract decussates at

none